1. Field of Invention
The present invention relates to a spring clutch apparatus for a drive mechanism and more particularly, to a bi-directional spring clutch apparatus for a reducing worm gear drive.
2. Description of the Prior Art
In shiftable or reversing gear drives, such as are used in overhead conveyor systems, the driving element is typically engaged and disengaged from the driven element by a mechanically operated, dog-type clutching mechanism which is controlled by an external lever. Although this provides for positive engagement and disengagement, it also frequently results in jerky or uneven starts and stops. Likewise, in order to engage or disengage such mechanisms under load, significant loads on the control lever are often required. This contributes to imprecise movements as well as wear and tear on all parts of the device or machinery to which the drive is connected.
In overhead and other conveyor type drives, particularly those designed for integration into automated or semi-automated manufacturing facilities, there is a need for a clutching mechanism for such drives which is bi-directional and is easily and efficiently engaged and disengaged under load. There is also a need for a clutching mechanism which operates smoothly and precisely while handling heavy loads.
In certain types of drive mechanisms, spring clutches have been used advantageously to engage or disengage a drive element and a driven element with less jerkyness and less effort, particularly when engaged or disengaged under load. A description of the basic operation of spring clutches is set forth in U.S. Pat. No. 4,433,765. An example of a drive mechanism employing a spring clutch of this nature is shown in U.S. Pat. No. 2,742,126. In this example, a plurality of springs are arranged in series in such a way that they begin to transmit torque after slippage, the amount of slippage differing from the first spring to the last, thus allowing the clutch to take up its full torque in smaller increments. French Pat. No. 755,404 shows a simple, single direction spring clutch mechanism used in connection with a worm gear drive.
Likewise, spring clutch mechanisms have been successfully used with bi-directional drives as well. A description of the basic operation of bi-directional spring clutches is set forth in U.S. Pat. No. 4,372,432. In this description, however, only one spring is used.
Application of bi-directional spring clutches to drive mechanisms of various types is shown in U.S. Pat. Nos. 4,364,286, 3,361,235, 3,321,986 and 3,304,793. Japanese Pat. No. 53-13049 is also illustrative. U.S. Pat. No. 4,364,286 shows a bi-directional spring clutch used as a braking mechanism in connection with a pair of epicyclic gear trains. U.S. Pat. No. 3,361,235 shows a bi-directional spring clutch which permits transmission of torque from an input shaft to output shaft, regardless of the direction of rotation of the input shaft, but which prevents transmission of torque from the output shaft to the input shaft. U.S. Pat. No. 3,321,986 shows spring clutches as used in a bi-directional transmission. U.S. Pat. Nos. 3,304,793 shows a bi-directional spring clutch which permits transmission of torque by an input shaft which is driven in either direction of rotation or selectively prevents transmission of torque by the input shaft when a single tang, one from each spring, is interrupted by a stop. Japanese Pat. No. 53-13049 shows a similar arrangement using four (4) springs. This mechanism is also capable of transmitting torque in both directions or not transmitting torque at all, depending on whether a single tang, one on each spring, is engaged by a stop mechanism.